ANNUAL LEGUME COVER CROPS IN SPRING WHEAT-FALLOW SYSTEMS

Soil erosion is a problem in conventional tillage spring wheat (Tritic um aestivum L.)-fallow rotations in semiarid regions. Early research u sing legumes to provide surface cover for erosion control in dryland c rop rotations showed no yield benefits to a succeeding crop. Better re sidue management practices have improved fallow soil water storage and could reduce detrimental soil water influences of legumes to a succee ding crop. Objectives of our research were to determine whether field pea (Pisum sativum. L.) and Tangier flatpea (Lathyaus tingitanus, L.) could be grown during part of the fallow period in a hard red spring w heat-fallow rotation to provide dry matter (DM) and surface cover for erosion control and to evaluate the influences of legumes on a succeed ing spring wheat crop, Legumes were seeded during the fallow phase of a spring wheat-fallow rotation from 1989 through 1992. During dry year s, total DM and surface cover were reduced more for Tangier flatpea th an field pea. Legumes produced sufficient DM to exceed 35% surface cov er by the flowering plant development stage when precipitation was not limiting. If growing conditions were good, legumes used soil water to a depth of 5 ft when legume growth was terminated at pod formation or grown for the full season, The N contribution to a succeeding spring wheat crop was not evident in grain N concentration or uptake, When le gume growth was terminated at or before flowering, legumes provided su fficient DM and surface cover to control erosion without consistent de trimental influences to a succeeding wheat crop.